This invention relates to a generator voltage regulating system and more particularly to a system and method used to stabilize the voltage regulating system using load response control.
Voltage regulating systems are used in many applications to hold an electrical system's operating voltage within a predefined window. The voltage regulator system is particularly useful in applications, such as automobiles, where the system voltage must remain within a predefined window, but the electrical load may vary, for instance when the operator turns on or off different accessories in the vehicle. The voltage regulator allows the vehicle to operate within a system voltage window (typically 12-15 V) while providing varying levels of power to run all of the accessories requested by the operator.
FIG. 1 illustrates a simplified electrical system 100 used in many automobiles. The system includes a battery 110, an electrical load 120, a voltage regulator 140, and an alternator 160. By means of a crankshaft 170, the vehicle's engine 180 operates to spin a rotating coil in close proximity to stationary coil enclosed within the alternator 160, thereby inducing a current within the stationary coil of the alternator 140. The induced current is then rectified and delivered to the load 120 or to the battery 110 when needed.
The voltage regulator 140 holds the operating voltage of the electrical system 100 within a specific range, typically 13-15 VDC by controlling the amount of current the alternator 160 supplies to the system 100. The voltage regulator 140 senses the system's voltage and varies the alternator output current accordingly to keep the electrical system's voltage within the desired operating range. When the amount of current required for the vehicle's operation changes, for instance when the operator activates the climate control or when the battery 110 is in need of recharging, the voltage regulator 140 controls the alternator 160 to deliver more current so that the system voltage remains within the desired range. Similarly, the voltage regulator 140 controls the alternator to deliver less current when required, for instance when an accessory is de-activated.
Automotive vehicles are electrically very noisy environments and the described voltage regulator system is susceptible to noise occurring at the input of the voltage regulator 140. When this occurs, the noise can cause severe fluctuations in the amount of current supplied to the electrical system, resulting in spontaneous engine acceleration or stalling.
One technique for stabilizing the voltage regulator and improving the voltage regulator's noise immunity is to increase the resolution of digital to analog converters (DACs) implemented within the voltage regulator. However, there is a substantial cost incurred in increasing the bit resolution in DACs, for instance from an 4-bit DAC to an 8-bit DAC. What is needed is a low cost system and method for reducing the amount of noise induced effects of the voltage regulator.